Chain driven bicycle drive trains have existed for many years. Generally the chain receives power input from a peddle crank that has a motive force exerted upon it from a rider's legs. The force is transferred by the chain to the driven wheel by one of a plurality of geared cogs, for example, which is in turn mechanically linked to a hub. The hub is attached to the drive wheel by means of spokes or solid inserts such as in the so-called disk wheels. In this way linear force from a rider's legs is transformed to rotational force applied to the wheel and then to the road surface.
From time to time the wheel must be detached from the bicycle frame, for example, to change a flat tire or to replace a worn part. There exist many contemporary methods for attaching the wheel to the bicycle frame. One method uses a solid axle threaded on both ends. Once the axle ends have been located correctly in the frame lugs, a pair of nuts are tightened to fix the wheel in place. A second method uses a hollow axle through which a rod, or so called skewer, is run. One end of the skewer has a lever and the other end an adjustable nut. Once the wheel is in the correct position the lever is operated which results in a clamping force to fix the wheel in place.
While these methods are functional, they suffer from a common flaw. The chain must be disengaged from the drive cogs in order to remove the wheel. Depending on the complexity of the cogset, this can be a messy and time consuming operation. For example, consider a ten speed cogset typical of contemporary road or mountain bicycles. In order to remove the wheel the chain must be driven to the smallest cog in order to provide the requisite slack chain tension to allow the wheel to drop away from the frame. Once done, the derailleur mechanism, which is used to move the chain up and down the cogset, must be held out of the way so that the cogset, which is attached permanently to the wheel, will have the needed clearance to drop away from the frame lugs.
Once the wheel is clear, maintenance can occur. But the same problems exist upon remounting of the wheel. First the derailleur must be moved out of the way, then the chain must be manually placed on the correct cog, then the wheel carefully moved into the frame lugs and the securing mechanism engaged. One major problem with prior art methods is that it is difficult to ensure the proper alignment of the wheel in the frame lugs. This happens in part because the chain exerts an off-axis load on the cogset which tends to make the wheel align off center. The result is that the wheel may then interfere with the brake mechanism causing an unwanted drag.
A second major problem with prior art methods is that the derailleur is very delicate. If the user inadvertently applies a force in the wrong place, the alignment of the derailleur box could be affected. This is so because the derailleur is essentially a parallelogram that moves the chain left or right depending on the rider's selection of gear. Any misalignment will cause difficulty in shifting. Finally, since the chain is now on the smallest cog, the shifter mechanism must once again be operated to place the chain on a cog that will allow a rider to easily get moving.
What would be desirable is an axle apparatus that forms essentially a solid axle when in place, but that eliminates the need for the user to deal with the chain or cogset when the wheel must be removed from the frame. The apparatus of the present invention provides an improved axle that accomplishes this goal yet still permits wheel mounting/dismounting without the need to manipulate the cog cluster and associated drive train components.